Brakes are standard features on powered wheel chairs to provide the user a positive control for bringing the chair to a stop from its travel mode. Some wheel chair braking systems are provided by de-energizing the motor, which by itself brings the wheel chair to rest. Other breaking systems place friction on the chair wheels if the joystick is put in neutral. These systems serve convalescents or those who have lost arm and leg locomotion and are not able to apply manual braking force directly to the rotating wheel hub.
An example of manual breaking is described in U.S. Pat. No. 6,315,085. A semi-automatic brake applicator comprises linkages that translate pivotal motion of an actuator lever to cause an actuator rod to move linearly, driving a clamp to cause a brake shoe to engage. Another system is disclosed in U.S. Pat. No. 5,799,756 in which the brake actuation is provided by a rotatable disc connected concentrically to the hub. Linkages attaching the rotatable disc to the brakes engage the brakes in one rotation position and disengage the brakes in another.
The two known exemplary braking mechanisms described are actuated by deliberate application of some force or motion on the user's part. An example is mechanical means responsive to the user getting out of the chair. This exiting movement causes brakes to be applied. In the embodiment shown, the weight of the user on the wheel chair seat places a brake mechanism in release mode allowing the chair to move. When the user raises out of the chair, thus removing weight from the chair seat, the brake is caused to engage, stabilizing the wheel chair for safer entry and egress.
Another example is a motorized wheel chair in which three separate safety braking mechanisms actuate upon the occurrence of a particular event. One safety mechanism is sensitive to changes of floor slope or surface elevation to stop the motor, which then acts as a brake. A second switch is sensitive to impact of the moving wheel chair with another object, to cut power. A third switch may be activated remotely to stop the wheel chair.
One condition which these and other prior art wheel chair safety-braking mechanisms do not adequately address, is the case of a user who for some reason has lost the capacity to control the wheel chair while in the midst of travel. Such circumstances are not uncommon with users who are subject to periods of light-headedness owing to medications; or persons subject to seizures; or persons who have lost some use of their arms or limbs and cannot readily react to conditions where braking is needed.